The present invention relates to a clutch assembly and particularly to a clutch assembly having a bearing component. More particularly, the present invention relates to a sleeve bearing within a clutch assembly which requires continual lubrication while the clutch assembly is running.
Various clutch assemblies are available which include some type of bearings or bearing assemblies. The bearings are kept lubricated while the clutch assembly is running in order to minimize the friction between the parts as much as possible. The lubricant most often used in a clutch assembly is a type of grease or oil.
According to the present invention, a bearing assembly includes a rotatable hub and a porous bearing surrounding the hub, a sprocket surrounding the bearing, and means for rotating the hub relative to the bearing. The porous bearing includes "lubricant channels" containing a lubricant and having inlet openings facing toward the sprocket and outlet openings facing toward the rotatable hub so that lubricant in the lubricant channels can exit through the outlet openings to lubricate the mating surfaces of the bearing and the rotatable hub. The porous bearing is permeable to fluids and thus capable of being penetrated by lubricants and greases and thus due to its porous character includes lubricant channels that function to conduct lubricants and greases from an outer surface of the porous bearing to an inner surface of the porous bearing through lubricant channels or pores formed in the porous bearing.
The sprocket includes a reservoir containing a grease which becomes fluid at a certain melting temperature and is thus able to pass out of the sprocket reservoir and through an annular space between the sprocket and the bearing into the lubricant channels formed in the bearing. Rotation of the hub relative to the bearing and the sprocket generates enough heat (that is transferred through the bearing to the grease reservoir) to melt a portion of the grease carried in the reservoir formed in the sprocket. Some of the melted grease flows out of the reservoir into the lubricant channels or pores formed in the bearing to replace lubricant that has evaporated from an interface between the bearing and the rotatable hub during rotation of the hub relative to the bearing. This transfer of grease from the sprocket reservoir to a bearing/hub interface through the lubricant channels or pores formed in the bearing takes place slowly over a long period of time so that the bearing/hub interface is lubricated continually by the grease transferred from the sprocket reservoir as the hub rotates relative to the bearing and the sprocket and heat is generated to melt some of the grease in the sprocket reservoir and the melted greases passes into and through the porous bearing to reach the bearing/hub interface.
In preferred embodiments, the sprocket includes a tubular member having a cylindrical inner surface defining a passageway containing the bearing and an outer surface carrying sprocket teeth. The porous bearing is an elongated sleeve bearing surrounding the hub so that the hub is mounted for rotation within a passageway formed in the bearing. The bearing is mounted in the sprocket passageway so that inlet openings in the lubricant channels or pores formed in the bearing always face toward the cylindrical inner surface and outlet openings in the lubricant channels or pores always face toward the rotatable hub.
Two annular grooves are formed in the tubular member of the sprocket and arranged to open into the passageway containing the bearing to provide the grease reservoir in the sprocket. These annular grooves are arranged to lie in spaced-apart relation to one another along the length of the bearing so that one annular groove is near to a first end of the sleeve bearing and the other annular groove is near to a second end of the sleeve bearing.
The two annular grooves are filled with a bearing grease that becomes fluid in the presence of heat generated by rotation of the hub within the passageway formed in the bearing. As the hub is rotated, heat passes through the non-rotating bearing to reach the bearing grease in the grease reservoir and heated fluidized grease passes out of the grease reservoir defined by the two annular grooves formed in the sprocket into and through the lubricant channels or pores formed in the porous bearing to reach the bearing/hub interface to ensure that the bearing is lubricated properly as the hub rotates relative to the bearing and sprocket even as original lubricant evaporates and leaves the bearing/hub interface.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.